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Cracking of the concrete decks on newly constructed bridges in Minnesota has become a significant concern. Since 2005 MnDOT has been collecting bridge deck construction and early age cracking information on a "Bridge Deck Placement Data Form." The information collected has been entered into a database, along with early age crack surveys, concrete mix design information and concrete testing information. There currently is information on over 120 bridges stored in the database. Crack surveys were performed on 20 of the bridges contained in the database. A statistical analysis of the data, including the updated crack surveys, was performed to determine if there were any relationships between variables collected on the forms and crack frequency, type, or time of development. The analysis showed that, in general, the data collected was not sufficiently consistent to draw significant conclusions. A relationship for temperature restraint cracking for bridges with integral abutments was developed for lineal feet of cracking as a function of bridge deck age, water/cementitious material ratio, and total cementitious content. Recommendations were made for modifications to current construction practices and improving the uniformity of the data collected on the "Bridge Deck Placement Data Form" in the future, so that additional analysis could be performed with more consistent data.

Thin polymer overlays (TPOs) enhance the safety of bridge decks by increasing skid resistance; but they also act as barriers to chloride ingress. TPOs are often applied to concrete bridge decks before they are opened to traffic and have a 10-to 15-year service life. It was hypothesized that delaying the application of the TPO and allowing some chlorides to penetrate the deck would not compromise the service life of the bridge deck and offset the application and repair costs. A program modeling chloride ingress was developed to predict the optimum time for TPO application to prevent chloride concentration from reaching threshold concentration and maximize the service life of the first TPO. The program works in Microsoft Excel to model chloride distribution from a surface boundary condition using Fick’s second law and finite difference method. Although the method is not new, MnDOT’s implementation is tailored toward common bridge deck preservation activities and modeling needs. The appendices within the report walk through most usage examples in lieu of a manual. NOTE: The Excel macro file is 120 MB in size and may be accessed from https://edocs-public.dot.state.mn.us/edocs_public/DMResultSet/download?docId=15417346

MnDOT and Aggregate Ready Mix Industries of Minnesota constructed a 6 “ thick 60 ft X16 ft pervious concrete pavement on a 12” thick, Coarse Aggregate CA-50 Base at MnROAD in September 2005. Prior to this a pervious granular layer, and pavement instrumentation were placed. This driveway was made up of sections representing 3 different mix designs placed 6 inches thick with one joint grooved into the pervious concrete while it was still in a plastic condition and a second joint that was constructed as a temporary header during the placement operation. To facilitate sampling without compromising the pervious matrix, replicate test pads of two mix designs were constructed on the east side of the Driveway. For destructive testing, cores will be taken from these pads periodically. This project will help answer the following questions. • What is the Permeability change over a winter? • Does sanding and salting affect the permeability? • Does the surface ever get ice when the other surrounding surfaces do not? Bituminous and concrete pads are next to the Pervious Driveway. • Can the Pervious Concrete withstand the environmental effects of a winter under sanding and salting conditions? • What is the number of freeze thaw cycles monitored in the Pervious Concrete? This study is expected to produce valuable research results after the first 2 winters. The report also discusses yield, and workability as well as hydraulic modeling issues germane to pervious concrete.